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17.4 Sound and Hearing

Properties of Sound Waves
Intensity and Loudness
  • Loudness is a physical response to the intensity of sound and is modified by physical factors.
  • Intensity is the rate wave energy flow through an area
  • when loudness increases, intensity increases
  • when loudness decreases, intensity decreases
  • sound intensities are measured in decibels (dB)
  • Decibles are based off powers of 10

Frequency and Pitch
  • Frequency of sound as you perceive it.
  • Frequency is how fast a source is vibrating
  • Pitch depends on age and health of your ears
  • examples: Trumpet and French horn
  • if their is high frequency then their is high pitch
  • if their is low frequency then their is low pitch
SpeedTrumpet.jpg
  • at 20 degrees celcius the speed of sound travels at 342 m/s
  • sound travels fastest in solids, slower in liquids, and slowest in gases

Uses
Ultrasound
  • is used in a variety of applications including sonar and ultrasound imagery
  • example: to look at babies or your heart
  • Sonar helps determine the distance to an object underwater
  • it is calculated using the speed of sound in water and amount of time an echo is
ultrasound.jpg
Doppler Effect
  • doppler effect is a sound frequency caused by a movement of the sound source, motion of listener, or both
  • Close=Higher pitch, Farther=Lower pitch
MusicAmbulance1.jpg
  • most instuments have different pitches by changing the frequency
  • resonance is the response of a standing wave to another at the same frequency
Hearing with Ears
  • the outer ear gathers sound to the middle ear, which then amplifies the vibrations. Then uses ear nerve endings to the brain.
hearing_with_ears.jpg